Destroy 20 Scourge of any type at Talramas and the Festering Pools. Then, return to Sage Highmesa just to the south of The Dens of the Dying.
20x Talramas Scourge Destroyed
The fallen necropolis to the west can only be assumed to still be filled with Scourge.
While you are at Talramas, [class], I would ask that you dispatch all of the Lich King's servants that you find within and in the surrounding pools where it fell.